The amount of private funding received by the group edged up slightly this year to $4.5 billion, from $4.1 billion in 2010.

The No. 1nonprofit on the list was the United States Fund for UNICEF, same as last year. This year, however, the charity grew its operating expenses to $442.9 million from $429.8 million. Last year, UNICEF had to cut its budget.

The other groups in the Top 5 were the International Rescue Committee, the Institute of International Education, the Metropolitan Museum of Art and the Metropolitan Opera Association. The Metropolitan Opera jumped up two slots in the rankings from last year, reporting operating expenses of $299.1 million.

The biggest gainer on this year's list was at Teach For America. It jumped to No. 12 from No. 18, on the strength of a $43.5 million, or 24.7%, increase in expenses from 2010. The nonprofit, which recruits graduates from the country's top schools and places them in low-income public schools to teach for two-year stints after college, has been growing for the past few years, fueled by the trend towards education reform. This fall, the group increased the number of incoming teachers by 13% to 5,100. A record 50,000 graduates applied for those spots.

Teach For America was able to increase fundraising by around 26% last year to fund its growing program, despite losing a $21 million federal grant. It received a five-year, $50 million grant from the Walton Family Foundation earlier this year, among other large gifts.

With momentum growing in both fundraising and graduate interest, the organization is on track to double in size over the next few years, putting 15,000 teachers in 60 of the highest poverty areas in the country.

“One silver lining of the recession is that it's given college seniors a chance to think differently about what they want to do,” said Eric Scroggins, executive vice president of growth, development and partnerships at Teach For America.

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